Yep, those bess' will shoot. Try a .715 mould to cast alloyed lead balls. Balls cast from an alloy generally come out a few thou larger and fit the bore better. A .718 ball with an .018-.020 patch will still thumb start and shoot accurately to at least 75 yards.
I have won my share of smoothbore matches with that old Ped bess.
It has proven itself during military matches to about 75 yards, shooting at rectangular steel plates, the size of a kill zone on a man, supported on vertical angle iron stands, to chest height. a number of these targets, usually 5, or so in each bank, are lined up in ranks at 75 yards. One team of Brits and one team of frenchies in formation fires volleys at their respective targets. Each time a target is knocked down, one man corresponding to the target on the opposing team, i.e. the first man on the right, if the right hand target is "killed", is eliminated. One or two volleys are fired at each range, with each team moving forward 10 yards, in military fashion, to fire another volley until the opposing team is "killed". The fenchies didn't like to compete against our Ranger company. They said we cheated by "practicing" throughout the year. Our practice consisted of hunting, trekking, and competing at whatever events we could attend. They, on the other hand, primarily attended battle reenactments, firing live rounds only a few times a year.
These matches are LOTS of fun, and that big ball hits that steel with authority.
God bless